Optical wavelength converter device

Abstract

A light source device that converts a beam of light radiated from an optical fiber-type second-harmonic generating element to a parallel beam of light filled with a bundle of rays up to a central portion of the parallel beam by causing a portion of the beam of light to pass through an apex of a conical surface. The light source device is unlikely to be affected by the spherical aberrations of members constituting an optical system such as lenses, which makes it unnecessary to make the component members of the optical sysem special, thereby simplifying the optical system.

We claim: 
     
       1. An optical wavelength converter device comprising: a laser light source;   a second-harmonic generating means for generating a second-harmonic of laser light from said laser light source incident thereupon; and   lens means for converting a beam of light radiated from said second-harmonic generating means to a parallel beam of light filled with a bundle of rays up to a central portion of the parallel beam, said lens means comprising at least one conical surface having an apex, said lens means being arranged in such a manner that at least a portion of the beam of light radiated from said second-harmonic generating means passes through said apex.   
     
     
       2. An optical wavelength converter device according to claim 1, wherein the second-harmonic generating means comprises an optical fiber-type second-harmonic generating element. 
     
     
       3. An optical wavelength converter device according to claim 2, wherein the lens means comprises a collimator lens having a plurality of circularly symmetric, inclined surfaces, at least one circularly symmetric, inclined surface is formed as a conical surface having an apex, and said collimator lens is arranged in such a manner that at least a portion of a beam of light radiated from said second-harmonic generating means passes through said apex. 
     
     
       4. An optical wavelength converter device according to claim 3, wherein the collimator lens comprises two convex conical surfaces. 
     
     
       5. An optical wavelength converter device according to claim 3, wherein the collimator lens comprises a convex conical surface and a concave conical surface. 
     
     
       6. An optical wavelength converter device according to claim 3, wherein the collimator lens comprises at least one conical surface with an apex cut off flatly. 
     
     
       7. An optical wavelength converter device according to claim 2 wherein the lens means comprises three conical surfaces, at least one conical surface having an apex, and said lens means is arranged in such a manner that at least a portion of a beam of light radiated from said second-harmonic generating means passes through said apex. 
     
     
       8. An optical wavelength converter device according to claim 7, wherein at least one conical surface has an apex cut off flatly.